1. Field of the Invention
This invention relates to safety edge assemblies for movable closures such as garage doors and more particularly, to an electrosensing edge for automatically reversing the downward movement of the door when the edge sealing member encounters an obstruction during closing. In a preferred embodiment the electrosensing edge includes an elongated metal bracket which is mounted on the leading edge of the door and the sealing member is suspended from the bracket and traverses the width of the door. A spring-loaded cable capable of carrying an electric current extends between two insulators located at each end of the metal bracket inside the sealing member and the cable acts as a switch which is normally open but is closed if the door strikes an object and the cable is consequently forced against the bracket, to ground. Accordingly, contact of the cable with the bracket between the insulating blocks closes an electrical circuit, trips a relay and causes the actuator to reverse downward movement of the door, without injury or damage to the object which it strikes.
Since the passing of 1995 Federal legislation that governs the parameters of safety devices installed on residential garage door operators, most manufacturers rely on a fail-safe photo cell system set up in conjunction with a load sensor on the motor. The load sensor on the operator will reverse the motor if the load increases past a pre-determined level. The system will also reverse if the photo cells are obstructed. Part of the fail-safe system designed into these operators is the ability for the system to detect a short in the photo beam wires. If the operator is in the downward mode and a short condition exists, the beam then becomes inoperable and the door reverses and travels to the open position. The safety edge of this invention is designed to create a short in these photo cell wires, which will create a condition that will reverse the door. The fail-safe adaptation feeds power to the photocells through the bottom safety edge. If an interruption in current were to exist, the photo cell setup will become inoperable, and the door will reverse if coming down and will not operate until current is restored to the photocells.
For many years, sensing edges have been used in the doors of garages and commercial and utility buildings to stop or reverse closing movement of the door in the event that the door encounters an obstruction. Originally, most garage or large commercial doors were manually operated, with large or extremely heavy doors counterbalanced to permit opening and closing by one person. The requirement for mechanical assistance in the operation of large doors in commercial installations and more recently, garage doors, has resulted in the use of electric motors to power the opening and closing of such doors. Along with the use of electric motors has arisen the safety concern of a power-operated door closing with a person, animal or object in the path of the door. This consideration prompted the widespread use of radio-operated remote control devices to actuate the closing and opening of such doors from a distance or from an obstructed vantage point where it is difficult or impossible to ascertain that the closing door is free of obstructions.
2. Description of the Prior Art
Generally, two approaches have been taken to implement mechanisms for stopping or reversing a garage door when an obstruction is encountered by the closing door. In one application, the motor or drive train effecting the closing and opening of the door is adapted to sense substantially increased resistance to closing of the door. While affording a degree of safety protection, devices of this type often require frequent and precise readjustment and are otherwise prone to malfunction. Another type of application utilizes the installment of a mechanical actuator, an electrical switch or a sensor on the leading edge of the door to engage any object which might be encountered during closing of the door and actuate suitable controls to stop and/or reverse the motor which drives the door. Typical of these edge-mounted sensing devices is the "Astragal for Closure Members" described in U.S. Pat. No. 5,259,143, dated Nov. 9, 1993, to Albert W. Mitchell, et al. The astragal is characterized by an elongated, arcuate sealing member which traverses the leading edge of a closure such as a garage door, a pair of electrically-conductive strips extending the length of the sealing member in vertically-spaced relationship and a switch electrically connected to the conductive strips for reversing downward movement of the door in the event that the sealing member engages an obstruction and the conductive strips contact one another. U.S. Pat. No. 5,260,529, dated Nov. 9, 1993, to Bearge D. Miller, discloses a "Sensing Edge For A Door Including A Switch And Flexible Protruding Sensing Members", which includes an elongated, flexible sheath which is attached to the leading edge of a closure such as a garage door. A switch provided in the sheath operates to reverse the direction of travel of a closing door after the door strikes an obstruction. A "Sensing Edge" is disclosed in U.S. Pat. No. 5,262,603, dated Nov. 16, 1993, to Bearge D. Miller. The sensing edge is characterized by a base member which is secured to the leading edge of a door and a sheath having a pair of upper and lower internal cavities traverses the length of the sheath and the bottom sheath receives a pair of upper and lower electrical contacts. Contact of the closing door with an obstruction causes the electrical contacts to engage each other and operate the door actuator to automatically reverse the direction of travel of the door. An electrical connector positioned in the sheath connects the electrical contacts to provide a fail-safe feature for detecting electrical problems in the electrical contacts. U.S. Pat. No. 5,384,982, dated Jan. 31, 1995, to Anatoly Galperin, describes a "Sensing Device Having Universal Interface For Cooperation With Plurality of Door Actuators". The sensing edge includes an elongated, flexible sheath mounted on the leading edge of a door and a pair of generally parallel, vertically-spaced contact members are disposed in the sheath and electrically connected to the door actuator. A termination circuit, electrically connected to the contact members, continuously generates a predetermined output voltage which is applied through the contact members to the actuator to facilitate selective closing of the door by the actuator. Upon application of a force to the sensing edge, the contact members contact each other to pr event the termination circuit output from being applied to the actuator, thereby causing the actuator to stop or reverse the direction of movement of the closing door. U.S. Pat. No. 5,438,798, dated Aug. 8, 1995, to Gunter Plamper, et al, details a "Safety Edge Assembly For A Movable Closure", including an electrically-conductive mounting rail which is mounted on the leading edge of the door. A deformable tubular member is suspended from the mounting rail and a conductive member on the tubular member is movable from a first position normally spaced from the conductive mounting rail into a second position engaging the conductive mounting rail, to complete an electrical circuit for reversing the t ravel direction of the closing door upon deformation of the tubular member. A "Power Door Safety Sensing Strip" is disclosed in U.S. Pat. No. 5,589,811, dated Dec. 31, 1996, to Robert Pariot, et al. The power door safety sensing strip includes a Z-shaped support bracket which is attached to the face of a power-operated garage door, and a flexible, tubular insulating member is suspended from the support bracket a short distance beyond the bottom edge of the door. A flat insulating member extends vertically from the support bracket, through the interior of the tubular insulating member and conductive surfaces on the flat insulating member and interior of the tubular insulating member are moved into contact upon deformation of the tubular insulating member, thereby reversing the direction of travel of the closing door. U.S. Pat. No. 5,602,370, dated Feb. 11, 1997, to David Kau, details a "Safety Switch For Electric Rolling Doors", including a plastic follower bar fastened to the bottom rail of an electric-powered rolling door and having two ribs on the inside of the follower bar. Two metal sheets mounted inside the follower bar above the ribs are separated by a slotted insulator sheet, and two actuators are fastened to opposite ends of the bottom rail of the electric rolling door. Each actuator includes a top plate fastened to one end of the bottom rail and two crossed pressure bars pivoted to the top plate. When the follower bar or actuator contacts an object during closing of the door, the follower bar is deformed to force the ribs upwardly against the metal sheets, which contact each other through openings in the insulator sheet and cause termination of the power supply to the electric motor powering the door.
An object of this invention is to provide an electrosensing edge of high reliability for automatically reversing closing movement of a door when the door encounters an obstruction.
Another object of this invention is to provide an electrosensing edge which is mounted on the leading or bottom edge of a vertical door such as a garage door and senses the presence of an obstruction in the path of the closing door, thus causing the door actuator to quickly reverse downward movement of the door and prevent injury or damage to the obstruction.
Still another object of this invention is to provide an electrosensing edge for an automatic, vertically-operated door, which edge includes an elongated, metal mount bracket that extends along the leading or bottom edge of the door, a typically rubber or plastic sealing member suspended from the mount bracket and a spring-loaded electrical cable extended between two insulators located at each end of the bracket inside the sealing member and acting as a switch which is normally open, but is closed if the door strikes an obstruction and the cable is forced against the mount bracket, thereby grounding the circuit and reversing downward movement of the closing door without injury or damage to the obstruction.